Transducers are known that perform conversion between mechanical energy and electric energy such as actuators and sensors and that perform conversion between acoustic energy and electric energy such as speakers and microphones. In order to form a highly flexible, compact, and lightweight transducer, polymer materials such as dielectric elastomers are useful.
For example, as disclosed in Patent Document 1, an actuator can be formed by arranging a pair of electrodes on both sides in the thickness direction of a dielectric film formed of a dielectric elastomer. In actuators of this kind, when a voltage applied between the electrodes increases, an electrostatic attraction between the electrodes increases. The dielectric film interposed between the electrodes is thereby compressed in the thickness direction, leading to a reduced thickness of the dielectric film. When the film thickness decreases, the dielectric film accordingly expands in a direction parallel to the electrode surfaces. On the other hand, when the voltage applied between the electrodes is reduced, the electrostatic attraction between the electrodes decreases. A compressive force against the dielectric film in the thickness direction thereby decreases, and the film thickness increases due to the elastic restoring force of the dielectric film. When the film thickness increases, the dielectric film accordingly contracts in a direction parallel to the electrode surfaces. The actuator thus expands and contracts the dielectric film, thereby driving a member to be driven.
In order to increase a force and displacement output from the actuator by applying a high voltage, it is desirable that the volume resistivity of the dielectric film is high and that the resistance to dielectric breakdown thereof is high. As an elastomer material having high resistance to dielectric breakdown, silicone rubber is known.